1. Field of the Invention
This invention is in the field of liquid atomizers and particularly the field of liquid atomizers used for the burning of high viscosity residual fuels as in diesel engines, and gas turbine burners, and other burners.
2. Description of the Prior Art
To efficiently burn liquid fuels requires that the liquid be broken up into tiny particles and that these atomized particles be suspended within the combustion air mass so that a large area of liquid is created for fuel evaporation into the air mass. Liquid fuels of higher viscosity are more difficult to thusly atomize adequately since the liquid responds only slowly to the forces causing atomization. In prior art liquid atomizers, these atomizing forces are the aerodynamic forces produced when the liquid moves at a high velocity relative to surrounding air or other gas. These high relative velocities are created by injecting the liquid at high velocity into an essentially stationary air mass, as in many diesel engines, or by moving a gas mass at high velocity across a liquid stream, or by injecting the liquid at high velocity and concurrently moving a gas mass at high velocity across this injected liquid stream, as in air or steam atomizing nozzles used in boilers. These prior art atomizers suffer the defect that the atomizing force, which acts upon the liquid to break it up into small particles, acts also upon the atomizing gas to reduce the relative velocity between liquid and gas, and thus to reduce the atomizing force as atomization proceeds. To efficiently atomize higher viscosity fuels thus requires use of higher liquid injection velocities, and hence pressures, or use of larger masses of atomizing gas where prior art atomizers are used. References A, B, and C describe the atomization process and the effects of liquid viscosity.
Prior art diesel engines are capable of burning high viscosity, residual type fuels, such as Bunker C fuels, but only in engines of large piston diameter and hence of low engine speed and high engine weight. This deficiency of prior art diesel engines results from the use of a high-pressure injector to atomize the liquid fuel in order to spread the liquid out over the large area of contact with air needed for rapid burning. Increasing fuel viscosity retards atomization but this effect can be offset by using higher fuel injection pressures. Fuel viscosity and injection pressure can be increased in this way but only up to the point where the liquid fuel is sprayed on to the combustion chamber surface since such fuel impingement destroys the needed atomization. In this way for each engine piston diameter, or injection path length, there exists a maximum useable injection pressure and a corresponding maximum useable fuel viscosity. Hence we find small piston diameter truck and bus diesel engines requiring low viscosity fuels whereas large piston diameter marine diesel engines can use residual type fuels efficiently. Necessarily then high viscosity fuels are useable only in prior art diesel engines which are too heavy for use in trucks, buses or railroads since large piston diameter requires a low engine RPM to keep inertia forces reasonable and hence requires a high engine weight per horsepower.
This deficiency of prior art diesel engines has not been important in the past when low viscosity, distillate diesel fuels were readily available at low prices. But this is no longer the case, and it is now important to seek to utilize all kinds of liquid fuels for those transportation applications, such as trucks and buses, whose refueling and fuel handling requirements necessitate use of easily handled liquid fuels. These are also the transportation applications which require light-weight engines and hence require diesel engines of small piston diameter. It would be a great benefit to have available small piston diameter, light-weight engines capable of efficiently burning high viscosity, residual type fuels.
Prior art burners, such as for gas turbine engines or steam boilers, are capable of burning high viscosity fuels but only by use of large diameter burners or by use of large masses of atomizing gas, such as compressed air or high pressure steam. In some gas turbine applications, such as for aircraft, such large diameter burners are a disadvantage. In all cases the atomizing gas requirement is a disadvantage as costly to supply and reducing the efficiency. It would be a great benefit to have an atomizer for these high viscosity residual fuels which could be used efficiently in small diameter burners and which required only small quantities of atomizing gas.
Certain mechanical portions of internal combustion engines are already well known in the prior art such as the pistons, cylinders, crankshafts, etc. The term "internal combustion engine" is used hereinafter and in the claims to mean these already well-known combinations of cylinders, cylinder heads, pistons operative within said cylinders and connected to a crankshaft via connecting rods, valves and valve actuating means or cylinder ports, cams and camshafts, lubrication system, cooling system, ignition system if needed, flywheels, starting system, fuel supply system, fuel air mixing system, intake pipes and exhaust pipes, superchargers, torque control system, etc. as necessary or desired for the operation of said internal combustion engine. The term "internal combustion engine" is used hereinafter and in the claims to include also the already well-known combinations as described above, but wherein the cylinders, cylinder heads, pistons operative within said cylinders and connected to a crankshaft via connecting rods, valves and valve actuating means or cylinder ports, are replaced by a rotary engine mechanism combination, comprising a housing with a cavity therein, and plates to enclose the cavity, a rotor operative within said cavity and sealing off separate compartments within said cavity and connecting directly or by gears to an output shaft, ports in said housing for intake and exhaust, such as in the "Wankel" type engine. An internal combustion engine may be of the four-stroke type, wherein for each cylinder two full engine revolutions or processes are required to complete a single engine cycle of intake, compression, combustion, expansion and exhaust, or alternatively may be of the two-stroke type wherein a single engine cycle is completed, for each cylinder, within a single engine revolution or process, as is well known in the art of internal combustion engines.
The term, "internal combustion engine mechanism," is used herein and in the claims to mean all those portions of an internal combustion engine, as described hereinabove, except the fuel supply system, the fuel air mixing system, the torque control system, and any spark ignition apparatus. The terms, "piston" and "cylinder," are used herein and in the claims to mean these elements as commonly used in piston and cylinder engines, and also includes the functionally corresponding elements as used in other engine types such as the Wankel engine, and further includes cases where more than one piston is used in a single cylinder. The term engine cylinder is used herein and in the claims to include also the cylinder head if used.
The term "burner" is used herein and in the claims to mean those already well known combinations of combustion chamber, combustion air supply means, ignition means, fuel supply system, fuel flow control means, fuel atomizer means, fuel-air mixing system, etc. as necessary or desired for the operation of said burner. The term "combustion chamber" is used herein and in the claims to mean all those portions of a burner, as described hereinabove, except the fuel atomizer means and fuel flow control means.